Flexible film laminates wherein films of dissimilar polymeric materials are bonded together by an interposed adhesive layer to form a composite material are known and widely used in applications having performance criteria that cannot be met using a single film of either of the polymeric materials alone. For example, a polyester film may be bonded to a polyolefin film to provide a high-strength heat-sealable packaging material.
The adhesive layer of such laminates must develop a strong bond with each of the polymeric films of the laminate in order to resist delaminating stresses which may be directly imposed by the conditions of the end-use application and which may also arise from the dissimilar responses of the respective layers of the laminate to those conditions.
Furthermore, from the standpoint of providing an economically feasible and environmentally responsible method for manufacturing such flexible laminate materials, it is important that the adhesive layer cures rapidly at room temperature and does not require the use of volatile organic solvents.
U.S. Pat. No. 5,037,700 discloses a process for preparing a flexible laminate. The process involves the use of a room temperature curable adhesive that consists essentially of a copolymer emulsion of an alkyl (meth)acrylate, styrene or a vinyl ester and from 1 weight percent to 10 weight percent of an ethylenically unsaturated carboxylic acid in combination with an epoxy resin emulsion and a polyfunctional amine.
While the process disclosed in the U.S. Pat. No. '700 patent is said to provide a laminate characterized by superior bond strength, superior resistance to temperature extremes and superior resistance to chemicals and water, those skilled in the art will recognize that such claims are relative and that there remains an acute interest in laminates that exhibit properties superior even to those exhibited by those laminates made by the process of the U.S. Pat. No. '700 patent.